Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to fuel in-ection nozzles
for s-~pplying fuel to compresslon ~lition internal com-
busti~)n engines and of the kind c~mprising a hollow bodv
part, a valve assembly including a resiliently loaded
valve member and a seating, the valve assembly being loc-
ated within the body part with a va]ve head forming part
of the assembly being exposed at or beyond ons Qrd of the
body part, and a fuel inlet communicating with the inter-
ior of the body part. the arrangemen t bging SUC~ that in
use, when fuel under pressure is supplied to the inlet,
the fuel pressure within the body ~art acting upon the
components of the valve assembly will effect movement of
the valve head away from the body and the seating to per-
mit fuel to flow past the valve head and seating into in
use, the respective combustion chamber of the assoclated
engine.
In use, the nozzle is secured within a bore ir the
cylinder head of an engine so that fuel flowlng past the
valve head and seating is atomised and is injected dir-
ectly into the combustion space of the engine. The fuel
is supplied by an injection pump which operates in timed
relationship with the engine and which may supply fuel
to other nozzles of the engine. The rate of fuel flow
to the engine during the period of fuel delivery has a
bearing on the amount of noxious gas in the eng~ns exhaust
and it has been found that the rate of flow of fuel
through the nozzle should increase relatively slowly
at the start of injection and decrease as rapidly as pos-
sible at the end of injection.
It is known to incorporate various types of device
in the fuel conveying conduit between the pump and the
nozzle or even ~ithin the nozzls, which act to provide
the deslred initial rate of fuel flow. These devi-es are
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however, comple~ and therefore costly and generally com-
prise some form of valve whiGh lim-ts the initial
flow rate by prcviding tqmporary storage for some of
the fuel flowing from the pump. Since the type of
nozzle set out in the first paragraph is well known as
being a comparatively cheap form of nozzle as compared
with the more conventior!al form of nozzle in which the
valve member moves in a direction away from said one end
of the body part, it is not appropriate to have to provide
an expensive valve to control the rate of fuel flow.
The object of the invention is to provide a nozzle
of the kind specified in a simple and convenient form.
According to the invention a nozzle of the kind
specified includes an annular elongated part located
within the body part, said elongated part surrounding
the portion of the valve assembly lying within the
body part, said elongated part acting to define part of
the wall of a chamber to which fuel under pressure is
supplied from the inlet and from which fuel flows when
the head is moved out of contact with the seating, the
wall thickness of said elongated part being such that
the wall deflects during the initial delivery of fuel
to the nozzle thereby to stQre part of the initial f-low
of fuel whereby the initial rate of flow of fuel past
the valve head and seating will be at a reduced rate.
, . .
According to the further feature of the invention
said annular elongated part defines an annular space
with the surrounding body par~, said space in use being
substantially at atmospheric pressure.
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In the accompanying drawings:-
Figure 1 shows a diagram of a fuel system incorpor-
ating a nozzle in accordance with the invention,
. Figure 2 shows to an enlarged scale, the valve assem-
bly of the nozzle,
Figures 3, 4 and 5 are sectional side elevations
- showing various forms of the nozzle.
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Referring to Figure 1 of the drawings an engine fuel
system includes a pump 10 which in use is driven in
timed relationship with the associated engine. The pump
is provided with a plurality of outlets indicated at 11
and each of these outlets is connected to a respective
injection nozzle one of which is indicated at 12, by means
of a fuel supply line 13. The nozzle 12 in use, is
located within a bore formed in the cylinder head 14 of
the engine so that the inner end of the nozzle projects into
a combustion space of the engine.
Turning now to Figure 3 the nozzle 12 comprises a
body part which is formed in two parts 15, 16. The part
16 is of hollow form and is provided with a peripheral
screw thread for engagement in use, in the bore formed in
the cylinder head of the engine. In addition, the part
16 is provided with a hexagonal portion for engagement
by a spanner or the like to enable the nozzle to be
tightened within the aforesaid bore.
The part 15 is provided with a hexagonal section
intermediate its ends and on opposite sides of the hex-
agonal section, two sets of peripheral screw threads.
The part 16 is internally threaded to receive one of the
sets of screw threads on the part 15. ~oreover, the part
15 defines an annular skirt portion 17 which extends
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. within the part 16 for engagement with a flange 18 of
a valve assembly generally indicated in Figure 3 at 19,
the other side of the flange being urged when the parts
15 and 16 are tightened, into sealing engagement with an
inwardly directed end portion 20 of the part 16.
In addition, the part 15 is provided with a longitud-
inal passage 21 which is shaped at its outer end, to
receive the shaped end of the fuel line 13. The threads
at this end of the part 15 of the body are provided
for engagement by a retaining nut which acts to retain
the fuel line relative to the part 15.
It will be noted tha~ the skirt portion 17 defines an
outer annular space with the internal wall of the part 16 of
the body part and conveniently this space in uqe, comm-
unicates with the atmosphere by way of a passage (not
shown). The skirt portion 17 is of thin section for a
purpose to be described but it does act as part of the wall
of a chamber to which fuel under pressure is supplied by
: the injection pump .
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: In the arrangement shown in Figures 4 and 5 the
body part is of one piece construction and the valve
assembly 19 is held in position within the body part by
rolling over the end portion of the body part into
contact with the flange 18 after the valve assembly
.: has been located in the body part. It should be noted
however, that in the arrangement~ shown in Figuses 4 and
5 a separate annular member 22 is provided which corres-
ponds to the ~kirt portion 17 of the example ~hown in
Figure 3. As before, there is dèfined between the
annular =e=ber Z2 ard the wall o~` the body part, an
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annular space which communicates with the atmosphere.
.
The nozzle shown in ~igure 4 has a screw thread
whereby it can be secured within the bore and it is
also prov~d Wit}l a screw thread for engagement by a
nut for retaining the fuel line. In the arrangement
shown in Figure 5 the nozzle is devoid of scr~ threads
and it is held within the bore by a nut which also
serves to retain the shaped end of the fuel line in
contact with the body.
The valve assembly 19 will now be described with
reference to Figure 2. The flange 18 is formed on the
periphery of a tubular member 23 having an internal bore
24 which at its lower end is shaped to define a seating
25. Slidable within the bore is a valve member 26 having
at its end adjacent the seating a head 27 for co_operation
with the seating. Also provided on the valve member is
a helically fluted portion 28 which co-operates with
the wall of the bore to guide the movement of the valve
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member. Intermedia~Q the portion 28 and the head 27
the valve member is provi~ed with a recessed portion
29. Moreover, the tubular member is provided with a
pair of ports 30 adjacent its opposite end and these
communicate with the interior of the a~oresaid chamber
to permit fuel flow along an annular clearance 31
defined between the wall of the bore 24 and a length
of the valve member which is of reduced section.
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The valve member is biased to the closed position
i.e. the position shown in the drawings in which the
head 27 is in contact with the seating 25, by means of
a coiled compression spring 32 disposed between the
flange 18 and an abutment 33. The abutment 33 is en-
gaged about a portion of the valve member which extends
from the bore 24 and conveniently this is of two part
construction to facilitate the assembly thereof.
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.
In use, fuel supplied through the passage 21 acts
upon the valve member to urge the valve member downwardly
as shown in the drawings thereby lifting the head 27
from the seating 25. Such movement is of course against
the action of the spring 32. When this movement occurs
fuel from the chamber flows through the ports 30, along
the clearance 31 through the channels defined by the
fluted portion 28, through the clearance 29 and between
the valve head and the seating. $he fuel emerges from
the nozzle as a finely divided spray which is directed
into the combustion chamber of the engine.
As explained earlier in the specification it is
desirable that the initial rate of flow of fuel to the
combustion chamber should increase slowly. This is
obtained by allowing the skirt portion 17 or the annular
member 22~ to fle~ outwardly under the action of the press-
ure of fuel ~upplied through the passage 21. The wall thick-
ness therefore of the skirt portion 17 or the annular member
22 must be so chosen that the desired amount of flexure is
obtained for the particular application. Towards the end
of the period of delivery of fuel by the pump the pressure
reduces. During thi~ period the wall of the skirt portion
17 in the ~nnular member 22 regains its original dimension
and in so doing the volume of the chamber reduces thereby
expelling fuel from the chamber. The pump will incorporate
a delivery valve or a plurality of delivery valveq depend-
ing upon the type of pump, which act when the delivery of
fuel ceases, to unload the fuel line thereby allowing rapid
closure of the valve member 27 onto the seating 25,
